VO-DAS

Chenzhou CUIChao LIU, Haijun TIAN, Yang YANG,

etc

National Astronomical Observatories, CAS

VO Data Access Service (VO-DAS)

An OGSA-DAI based service system to provide unified access to astronomy data, including catalogs, images and spectra.

Goals of VO-DAS Supporting high volume data query Interlinking distributed and heterogeneous archives

• catalogs, images, spectrums Providing a software that works for astronomersworks for astronomers

First Science Paper from China-VO

Candidate Milky Way satellites in the Galactic halo （ Liu et al., 2008, A&A)

SDSS DR5 photometric data were searched for new Milky Way companions or substructures in the Galactic halo.

Data analysis procedures were based on the VO-DAS. Five candidates are identified as over-dense faint stellar sources that

have color-magnitude diagrams similar to those of known globular clusters, or dwarf spherical galaxies.

Predicted Features

Goals: Uniform access to heterogeneous distributed datasets, bulk of data support

Functions Catalog, image, and spectrum support Dataset encapsulating and registry Data discovery Metadata description Jointed query on heterogeneous databases Bulk of data transfer support Sync and async queries Query status tracer ADQL support

Architecture Components

VO-DAS server DataNode Clients Registry Data storage

Technical Highlights

OGSA-DAI based data nodeAsynchronous query and cross match on

distributed databasesExtended ADQL, supporting catalog, image

and spectrum at the same time

Async Query Query segmented into sub-

queries Queries assigned to specific

DataNodes Query results transfer among

DataNodes Final results sent to data storage

service (VOSpace, FTP, etc) VO-DAS server supervises the

whole process No data exchange between

DataNode and VO-DAS server

Extended ADQL

SELECT s.ra, s.dec, s.g-s.i gi, s.i FROM SDSSDR5:star s WHERE s.ra>=120 AND s.ra<=270 AND s.dec>=25 AND s.dec<=70 AND s.i>=19 AND s.i<=22 AND s.g-s.i>=0 AND s.g-s.i<=1

SELECT f.Access_reference FROM SDSSDR6:specfile f, SDSSDR6:sspParams s WHERE s.specID=f.specID AND f.SNR>10 AND s.alphafea<=0.2 AND s.feha>-0.9

VO-DAS Clients GUI CLI WebBrowser MATLAB Client

Interoperability

PLASTIC, SAMP

MATLAB based DM environments

AstroboxAstrobox

AstroBox A plug-in package for MATLAB to

provide an astronomical data mining application service, supporting VO protocols and tools.

A high-level data analysis environment supporting: PLASTIC VOTable Local DB VO-DAS client Astronomical algorithms

VO-DAS

MATLAB VO-DAS Client

MA

TL

AB

D

ata

base

Too

lbox

Local DBJa

vaLi

brar

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VO

Tab

les

PLASTIC

VO Tools(Aladin, TOPCAT)

AstroBoxAstroBox

MATLAB based DM environments (cont.)

Science case：Sub-structure study for the Galaxy

Methodology

Density count in area (ra=120~270deg, dec=25~70deg) where i=19~22 and g-i=0~1 in the SDSS DR5 (bin=0.2x0.2deg)

Obtained 524 over density areaCalculate CMD for each areaIdentify these CMDs by hands

Results

Work done by VO-DAS 70 millions records queried from

SDSS DR7 database Calculate CMD for each over

density area

Other tasks done by MATLAB

Lessons learned

Grid and SOAP based data access solution is feasible

Too complex to control

Low performance

Current: RESTful TAP DAS

Collaboration Environment

CSCW(computer supported cooperative work)

e-ScienceVO

Collaboration Enviroments

LAMOST DBs

Project Scientists

ObservationDB

SciDB (internal)

SciDB (public)

Scientific WGs

Papers

Public Users

Data Processing

Research Projects